1. Field of the Invention
The present invention relates to an apparatus and method for cell searching in a wireless communication system. More particularly, the present invention relates to an apparatus and method for performing cell searching based on a single type of complex sequences in an asynchronous wireless communication system in which a time synchronization of a base station is not required.
2. Description of the Related Art
A Wideband Code Division Multiple Access (WCDMA) system and a Long Term Evolution (LTE) system whose standardization is in progress are currently being commercialized as asynchronous communication systems. Since timing synchronization of a base station is not considered in the asynchronous communication systems, the asynchronous communication systems perform a significantly complex cell search operation in comparison with synchronous communication systems. The cell search operation is carried out to search for a cell IDentifier (ID) and to obtain a timing of a received signal. The cell ID is a code for identifying a cell to which a mobile station belongs.
The WCDMA system performs the cell search operation in three steps, that is, slot timing synchronization acquisition, frame timing synchronization and cell group ID detection, and cell ID detection. The LTE system performs the cell search operation in three steps, that is, slot synchronization and sub-cell ID detection, frame synchronization and cell group ID detection, and cell ID detection.
Since the three steps of the cell search operation are performed in the conventional asynchronous wireless communication system, different types of sequences having different characteristics are used for each step of the cell search operation in order to obtain detailed timing information and cell ID information. For example, for each step, the WCDMA system uses a Golay sequence, a Hadamard sequence, a code group sequence, and a gold sequence. In addition, for each step, the LTE system uses a Zadoff-Chu sequence, an m-sequence, a 2 Dimensional (2D) orthogonal sequence, and a 2D pseudo-random sequence.
When the different types of sequences having different structures and different characteristics are used for each step in the wireless communication system as described above, a receiver is equipped with a correlation unit and a sequence generator depending on each sequence in order to perform signal acquisition and detection. Therefore, there is a problem in that the complexity of implementation increases.